package client

import (
	"fmt"
	"net/url"
	"strings"
)

// invitePrefix is the versioned fingerprint every minted link carries
// (web/static/invite.js buildInviteFragment). Older links are bare T.
const invitePrefix = "e1."

// InviteLink is a parsed /join/... link: where to join, the secret T (never
// sent to the server), and the inviter's suggested pre-fill name (rides in the
// fragment for the same reason — the server must not see it).
type InviteLink struct {
	Base string // scheme://host origin
	T    string // the invite secret (base64url)
	Name string // suggested name ("" when the link carries none)
}

// ParseInviteLink parses a full invite link — https://host/join/<label>#<frag>
// — mirroring web/static/invite.js parseInviteFragment: the fragment is
// "e1.<T>" or "e1.<T>~<urlencoded name>" (bare T on older links).
func ParseInviteLink(link string) (InviteLink, error) {
	u, err := url.Parse(strings.TrimSpace(link))
	if err != nil || u.Scheme == "" || u.Host == "" {
		return InviteLink{}, fmt.Errorf("client: that doesn't look like an invite link (expected https://…/join/…#…)")
	}
	frag := u.Fragment
	if frag == "" {
		return InviteLink{}, fmt.Errorf("client: the link is missing its #secret — copy the whole invite link")
	}
	frag = strings.TrimPrefix(frag, invitePrefix)
	t, name := frag, ""
	if i := strings.Index(frag, "~"); i >= 0 {
		t = frag[:i]
		if n, err := url.QueryUnescape(frag[i+1:]); err == nil {
			name = n
		}
	}
	if t == "" {
		return InviteLink{}, fmt.Errorf("client: the link is missing its #secret — copy the whole invite link")
	}
	return InviteLink{Base: u.Scheme + "://" + u.Host, T: t, Name: name}, nil
}